Production of microbeads of pesticides and use of said microbeads for the protection of crops

Abstract

Process for the manufacture of microbeads of an at least partially water-soluble pesticide by polycondensation of complementary organic reagents R 1 and R 2 in a liquid two-phase system, the reagent(s) R 1 being placed with the pesticide in a polar liquid phase (ω p ) and the reagent(s) R 2 being placed in an oily liquid phase (ω o ) comprising a solvent (S) that is immiscible with the polar phase and at least one surfactant for dispersing the polar phase (ω p ) in the said oily phase (ω o ) with stirring, characterized in that the pair of reagents R 1 and R 2 is chosen in such a way that the polycondensation occurs in the polar liquid phase (ω p ).

1 . Process for the manufacture of microbeads of an at least partially water-soluble pesticide by polycondensation of complementary organic reagents R 1  and R 2  in a liquid two-phase system, the reagent(s) R 1  being placed with the pesticide in a polar liquid phase (ω p ) and the reagent(s) R 2  being placed in an oily liquid phase (ω o ) comprising a solvent (S) that is immiscible with the polar phase and at least one surfactant for dispersing the polar phase (ω p ) in the said oily phase (ω o ) with stirring, characterized in that the pair of reagents R 1  and R 2  is chosen in such a way that the polycondensation occurs in the polar liquid phase (ω p ).  
   
   
       2 . Process according to  claim 1 , in which: 
 (a) the solubility of the reagent(s) R 2  in the polar liquid phase (ω p ) is greater than the solubility of the reagent(s) R 1  in the solvent (S);    (b) the migration rate of the reagent(s) R 2  is such that the polycondensation occurs in the polar liquid phase (ω p ).    
   
   
       3 . Process according to  claim 1 , which comprises: 
 (a) preparing a polar liquid phase (ω p ) by mixing the pesticide and the reagent(s) R 1  in water and/or a polar solvent, and then    (b) dispersing this polar liquid phase (ω p ) in an oily solution (ω o1 ) of the surfactant(s) in the solvent (S) that is immiscible with the polar phase, with stirring, and    (c) introducing into the stirred dispersion an oily solution (ω o2 ) of the reagent(s) R 2 , thus bringing about the polycondensation.    
   
   
       4 . Process according to  claim 1 , in which the solvent (S) is a plant or mineral oil.  
   
   
       5 . Process according to  claim 1 , in which the polar solvent is methanol, ethanol, dimethyl sulphoxide, N-methylpyrrolidone, dibasic esters (DBE) or a mixture of these compounds with each other and/or with water.  
   
   
       6 . Process according to  claim 1 , in which the surfactant is an alkylated poly(vinylpyrrolidone).  
   
   
       7 . Process according to  claim 1 , in which the reagents R 1  and R 2  are capable of forming a polycondensate chosen from polyamides, polysulphonamides, polycarbonates, polyesters, polyurethanes and polyureas.  
   
   
       8 . Process according to  claim 7 , in which the polycondensate is a polyurea formed from a mixture R 1  of diamines and/or triamines in the polar phase and from a mixture R 2  of aliphatic diisocyanates and/or triisocyanates in the oily phase, at least one of the mixtures R 1  and R 2  comprises a trifunctional compound.  
   
   
       9 . Process according to  claim 1 , in which the mass ratio of the polar phase to the oily phase ranges between 10/90 and 70/30.  
   
   
       10 . Process according to  claim 1 , in which the molar ratio between the functions of the reagents R 1  and R 2  is between 10/1 and 1/100.  
   
   
       11 . Process according to  claim 1 , in which the mass proportion of surfactant in the formulation is between 1% and 10%.  
   
   
       12 . Process according to  claim 1 , in which the polar phase also contains a water-soluble salt.  
   
   
       13 . Process according to  claim 1 , also comprising at least one concentration step.  
   
   
       14 . Process according to  claim 1 , also comprising a step of adding a thickener and/or an anti-sedimentation agent and/or an anti-aggregation agent and/or an antimicrobial agent.  
   
   
       15 . Process according to  claim 1 , in which the pesticide is an insecticide.  
   
   
       16 . Suspension of microbeads of an at least partially water-soluble pesticide, obtained by a process according to  claim 1 .  
   
   
       17 . Suspension according to  claim 16 , in which the mass content of pesticide is between 1% and 70%.  
   
   
       18 . Suspension according to  claim 16 , in which the mass content of microbead polycondensate is between 10% and 90%.  
   
   
       19 . Use of a suspension according to  claim 16 , for the preparation of pesticidal formulations.  
   
   
       20 . Process according to  claim 1  in which the solvent is an aliphatic oil.  
   
   
       21 . Process according to  claim 1  in which the solvent is non-aromatic oil.  
   
   
       22 . Process according to  claim 1  in which the polar solvent is methanol alone or mixed with water  
   
   
       23 . Process according to  claim 1 , in which the surfactant is a poly(vinylpyrrolidone) alkylated with hexadecene.  
   
   
       24 . Process according to  claim 1 , in which the reagents R 1  and R 2  are capable of forming a polycondensate chosen from a polyurethane or a polyurea.  
   
   
       25 . Process according to  claim 1  in which the molar ratio between the functions of the reagents R 1  and R 2  is between 3/1 and 1/20.  
   
   
       26 . Process according to  claim 1  in which the mass proportion of surfactant in the formulation is between 2% and 8%.  
   
   
       27 . Process according to  claim 1  in which the polar phase also contains sodium thiocyanate water-soluble salt.  
   
   
       28 . Process according to  claim 1  in which the pesticide is an insecticide, methomyl.  
   
   
       29 . Process according to  claim 1  in which the mass content of pesticide is between 1% and 30%.  
   
   
       30 . Use of a suspension according to  claim 1  for the preparation of insecticidal formulations.